At the height of the Cold War, a small group of Army personnel monitored communications in Soviet-controlled East Berlin. They'd send the recordings back to NSA headquarters in Washington and — in many ways, are the precursors to the modern surveillance system that has become so controversial.

At the height of the Cold War, a small group of Army personnel monitored communications in Soviet-controlled East Berlin. They'd send the recordings back to NSA headquarters in Washington and — in many ways, are the precursors to the modern surveillance system that has become so controversial.